Fluid operated binary counter



P 1968 E. F. RICHARDS ETAL 3,399,829

FLUID OPERATED BINARY COUNTER 2 Sheets-Sheet 1 Filed May 4, 1965 EDWARD E RICHARDS WARREN B. DEPPERMAN CORNELIUS P. McKENZlE BY ATTORNEY I p 1968 E. F. RICHARDS ETAL 3,399,829

FLUID OPERATED BINARY COUNTER Filed May 4, 1965 2 Sheets-Sheet 2 FIG?) 22 ms fOUNT-UP INPUT 36 COUNT- nowu INPUT INVENTORS EDWARD E 'RlCHARDS WARREN B. DEPPERMAN CORNELIUS P. McKENZlE United States Patent 3,399,829 FLUID OPERATED BINARY COUNTER Edward F. Richards, Winter Park, Warren B. Depperman, Orlando, and Cornelius P. McKenzie, Gainesville, Fla., assignors to Martin-Marietta Corporation,

Middle River, Baltimore County, Md., a corporation of Maryland Filed May 4, 1965, Ser. No. 453,068 2 Claims. (Cl. 235-201) ABSTRACT OF THE DISCLOSURE This invention relates to a fluid operated binary counter stage utilizing first and second cascaded fluidic elements, with each element having means for producing a fluid jet deflectable between bistable output channels, and each element having control orifices by the use of which switching of its jet can be brought about. The first element can be powered by a pulsed fluid input, whereas the second element can be powered by a continuously pressurized fluid input. The output channels of the first element are connected to the control ports of the second element, whereas a jet pump is disposed in each output channel of the second element, and each jet pump is in turn connected by a feedback passage to a control port of the first element. The reduced pressure developed in a feedback passage is sufiicient to cause aswitching of the jet of the first element upon the initiation of an input pulse, but insufficient to switch the jet to the opposite output channel during the continuation of a pulse.

This invention relates to fluid operated systems and more particularly to binary counters and counter stages incorporating bistable fluidic elements utilizing the Coanda effect.

The growing interest of recent years in fluid analogs in the electronic components has led to the development of amplification, logic, control and computer systems employing pressurized fluid as the basic energy medium. In such systems the elemental control components typically incorporate a power nozzle from which a deflectable jet of pressurized fluid issues, and, in addition, one or more control ports or orifices capable of influencing the direction of deflection of the power jet. The degree of deflection of the power jet may be proportional to the influence exerted on it by the control ports or orifices. Alternately, the configuration of the fluidic components may be designed to provide a digital characteristic whereby the power jet is controllably deflected between discrete angular output positions.

Digital fluidic components often make use of the Coanda effect, that is to say of the propensity of a fluid jet to attach itself to a surface adjacent the jet and to flow along the surface until deflected therefrom by an external influence. This invention is concerned with binary counter stages and systems formed of purely fluidic digital components.

It is one of the objects of this invention to provide practical binary counter stages comprised entirely of pure fluid logic elements.

Yet another object of the invention is to provide a fluidic counter stage which is responsive only to the interruption and resumption of input pulses and which exhibits stability during prolonged input pulses without a tendency to oscillate.

A further object of this invention, is to provide a pure fluid binary counter stage capable of incorporating both countup and countdown capabilities.

By way of a brief summary of the invention in one of its embodiments, a binary counter stage is provided having two bistable fluidic elements, one passive ele- 3,399,829 Patented Sept. 3, 1968 ment intermittently powered by a pulsed fluid input, and an active element powered by a continuously pressurized fluid input. The active element provides a memory capability for the stage of the counter with which it is associated and is connected by a pair of feedback channels to control ports on the passive element. The feedback eflect is carefully proportioned to prevent a tendency to oscillate. The output of the active element is a series of switched fluid pulses having a frequency one-half that of the input pulse frequency supplied to the passive element. Any number of basic one-bit stages can be serially connected to form a binary counter with any desired capacity.

Although the scope of the invention is not intended to be limited except by the claims appended hereto, further details of the invention as well as additional objects and advantages thereof will be more clearly understood in connection with the following detailed description of certain preferred embodiments taken together with the accompanying drawings wherein:

FIGURE 1 is a partially schematic illustration of a simple binary counter comprising a pair of basic binary stages constructed in accordance with the principles of this invention;

FIGURE 2 is a partially schematic illustration of a fluidic binary counter stage constructed in accordance with the principles of this invention and incorporating countup and countdown capabilities;

FIGURE 3 is a partially schematic representation of an alternate embodiment of the invention similar in function to that of FIGURE 2 but incorporating fluid amplification; and

FIGURE 4 is a partially schematic illustration of a still further embodiment of the invention.

In FIGURE 1 are shown two stages 10 and 11 of a simplified form of binary counter connected in cascade. The illustration is partly schematic and partly pictorial, the fluid elements themselves being shown in double-lined channeled configuration whereas the fluid carrying interconnections between elements are represented by single lines to simplify the drawing.

There are many ways of constructing these fluidic elements and their interconnections. A simple construction technique is to mold the elements as shallow channels in planar base sections of plastic and to seal the channels with flat lids aflixed to the base sections. The channels may also be etched or pressed into a base material. Additional fluid connections to and between elements may be made by conduits intercepting particular channel sections from directions out of the plane of the fluidic elements. Indeed there is no requirement that the fluid elements be arranged in planes, although this tends to simplify their construction. The elements may be made in separate pieces or whole integrated fluid circuits employing large numbers of fluid elements and interconnections may be constructed as a single integral assembly. The mode of construction of these components and systems is, in fact, immaterial to the practice of this invention.

Wherever the terms element or stage are employed herein it is to be understood that these expressions do not necessarily signify that the elements or stages referred to are separable components of an assembly.

Each of stages 10 and 11 comprises a cascaded set of bistable fluidic elements 12 and 13 having fluid input chambers 14 and 15, respectively for receiving pressurized fluid and for discharging a jet or stream of fluid through nozzles 16 and 17 respectively. Purely as an aid in following the operation of the various elements in this and in the succeeding illustrations a drafting convention has been adopted herein. Those chambers which receive a continuous and uninterrupted flow of pressurized fluid are shown as round. Those which receive a pulsed, intermittent or discontinuous flow of fluid are shown square. In practice of course, the shapes of these chambers will ordinarily be dictated by engineering considerations.

When a power source, such as a bottle of compressed gas, is connected, for example, to the power input port 15 of the bistable fluidic element 13, the fluid jet will issue either through output channel 13A or through output channel 13B, but not simultaneously through both. Those skilled in the arts to which this invention pertains will recognize that the cause of this bistability is due to a phenomenon known as the Coanda effect, so named because of its discoverer Henri Coanda. A coherent stream of fluid injected through a nozzle into the space between two opposing surfaces causes a pressure drop in the zones between the stream and the opposing surfaces. This is because of the entrainment of fluid from these zones by the rapidly moving fluid stream. If either of the opposing surfaces is sufficiently close to the stream an unstable condition is created tending to draw the stream of fluid aside. As this happens and the zone between the fluid stream and one of the surfaces narrows, the pressure in the zone drops still further moving the stream against the Wall where it remains locked as long as the stream keeps flowing or until it is disturbed by an additional influence;

The fluid elements shown in FIGURE 1 are all bistable. That is, in element 13 the fluid jet is capable of being locked onto the outside walls of output channel 13A or of output channel 13B. The stream can be moved from one output channel to the other in either of two ways. This can be done by increasing the pressure between the stream and the wall to which it is locked, or by decreasing the pressure on the opposite side of the stream. Both methods are employed in the embodiments illustrated herein. Toward this end bistable elements 13 are provided with control ports 13C and 13D on the outlet side of nozzle 17.

Suppose that when power is applied to element 13 the jet issues from output 13A. The jet will remain in this position until an active positive pressure control signal from some suitable power source is applied to control port 13C, at which time the jet will switch from output 13A to output 13B. When the control signal is removed, the jet will continue to issue from output 13B. To switch the jet back to output 13A, a positive pressure control signal is applied to control port 13D. An element of this type can be used to provide a memory, since it will remain in its last commanded position.

The passive bistable element 12 also has two output channels 12A and 12B respectively and is provided with control ports 12C and 12D adjacent the outlet side of nozzle 16. The bistable element 12 in the first stage is intermittently powered by a pulsed fluid input. It is this pulsed input which constitutes the information signal fed to the counter and to which the counter is responsive.

Each of the output channels 13A and 13B is provided with a jet pump 21 and 23 respectively. These jet pumps are responsive to the flow of fluid in their associated output channels to develop low pumping pressures due to the entrainment of fluid therefrom. Suppose that the active element 13 is initially set such that the jet issues from output channel13A. The action of the jet pump produces a negative pressure in feedback channel 22, with which it is connected, as compared to the pressure in feedback channel 24 connected to jet pump 23. Because the feedback lines 22 and 24 are connected respectively to control ports 12C and 12D of the passive bistable element, the pressure differential is applied across the outlet side of nozzle 16.

When a pressure pulse is initially applied to input chamber 14, the resulting power jet is diverted by the existing pressure differential across nozzle 16 into channel 12A. Output channels 12A and'12B lead directly to control ports 13C and 13D, respectively, of the active element through control channels 26 and 28. Positive pressure differentials created across the power jet in the active element 13 switches the element to its opposite stable condition with the jet diverted through output channel 13B.

When this latter action occurs, jet pump 23 begins operating and creates a negative pressure in feedback channel 24 as compared with that in feedback channel 22. This effect would tend to switch the passive element 12 once again to produce an output in channel 12B, and might cause the counter stage 10 to oscillate. However, the pressure effects preferably created in lines 22 and 24 are deliberately selected to prevent any such oscillation. This can be done because of the fact that the pressure differential which is required between control ports 12C and 12D to switch an existing power jet from one output channel to the other is greater than the pressure differential necessary to select the output channel upon the initiation of the power jet. By selecting the magnitude of the feedback effects produced through the feedback channel to be just sufficient to determine that state of the first or passive element upon the initiation of its power jet, but insufficient to alter the state of the element during the duration of its power state, oscillation is prevented. The feedback effect may, of course, be adjusted as simply as by sizing the orifices of the jet pumps appropriately or by varying the flow resistance of the feedback lines until the desired level of feedback effect is achieved.

Consequently, the output channel 12A of the passive element remains active and the output channel 13B of the active element remains active until the pressure pulse initiated through input chamber 14 is interrupted. Proper operation in such instances is of course assured by sizing the feedback jet pumps and control line resistances such that the pressure differential appearing at the passive element control ports will not provide the critical flow required to switch the passive element after the jet has been established in either of its stable positions. Therefore, the output of the passive element 12 remains in output channel 12A and the output of element 13 at output 13B until the pulse is removed from 14.

When the pulse is removed the passive element output ceases, but inasmuch as the active element is bistable, it remains with its output at 13B. When a second pulse appears in the passive element 12, the pressure differential across the control ports 12C and 12D of the passive element is adequate to direct the jet to its other stable position and the output appears in control line 12B. This signal switches the active element output from 13B back to 13A, where it remains until a third pulse is received by the passive element. As before, the passive element does not now again switch since the reversed feedback is inadequate to switch an established jet. Therefore, when the second pulse is removed, the passive element is then set up to receive the third pulse and thereafter repeat the cycle described above.

From the above discussion it is seen that the output of the active element 13 is a series of pulses with a frequency one-half that of the input pulse frequency. Output 13A of the active element can be used to drive the succeeding stage and for this purpose there is shown a fluid connection 29 connecting output channel 13A of the first stage 10 to the input chamber 14 of the second stage to provide the pulsed input for its operation. Outputs 13B in each stage may be employed as a binary readout. Any number of the basic one bit stages can be serially connected to form a counter with any desired capacity. The active ele ment output which appears at output 13B may be used to indicate the binary count; an output at 13B of the first stage represents 2, output 13B of the second stage is 2 and the output corresponding at the Nth stage corre sponds to 2 The total count is then the sum-of all the 13B outputs. Each output 13A is used to drive a succeeding stage.

Suppose the counter is reset so that all active element outputs appear at 13A, then no 13B outputs are present and the output count is zero. When a pulse is applied to the input of the first stage it will switch the active element to output 13B and the output count is 2 or 1.-The output at 13A is removed but this does not change the state of any succeeding stage. When the second pulse appears, the first stage active element is switched back to output 13A which pulses the second stage and switches it to output 13B. This results in an output count of 2 or 2. The third pulse again switches the first stage but gloes not affect the succeeding stages, which produces an output count of 2 plus 2 or 3. The fourth pulse switches the first stage to output 13A which pulses the second stage and switches it to output 13A. This in turn pulses the third stage and switches it to output 13B, resulting in an output count of 2 or 4. This process continues until the capacity of the counter is reached.

This invention is not limited to the particular form illustrated in FIGURE 1. Certain modifications may be made in the system to enlarge its function. For example, to provide the capability not only to count up but also to count down additional logic components may be incorporated in each stage as shown in FIGURE 2. In this illustration those components which are operationally equivalent to those in the preceding illustration are designated by the same reference numbers, only one binary stage being shown. In this embodiment the output channel 13A of the active bistable element is not used to drive the succeeding stage, but channel 13B may still be employed as the binary readout to signal the condition of the stage. Monostable elements 31, 32, 33 and 34 have been added to the basic circuit. Each element has its own source of power, although all of the power sources can come from the same plenum.

The operation of elements 31 through 34-is similar to the foregoing except that they perform as monostable elements instead of bistable elements. In each of these elements, which are continuously powered, the jet always issues through the A output channel, which may be considered the ON channel, except when a control signal or pulse is applied to the single control port C. When this happens thepower jet is diverted to the B or OFF output channel, but returns to output A when the control signal is removed or interrupted.

The control ports 31C and 32C of the first two monostable elements are connected through control channels 26 and 28 to the respective output channels 12A and 12B of the passive bistable element. Hence, one of the monostable elements 31 and 32 remains in its stable state or ON and theother in its unstable state or OFF depending upon which of the output channels 12A or 12B is active.

The control ports 33C and 34C of the next two monostable elementsare connected to respond to fluid flow in monostable output channels 31A and 32A respectively. Output channels 33A and 34A are connected to a common output line 39 to provide the pulse input to the next stage of the counter.

Additional input sources 35 and 36 are connected to control ports 33C and 34C respectively to provide countup and count-down capability, it being understood that each stage of the counter is provided with similar input sources. Input 35 when on, that is, when supplying a positive control pressure determines the count-up operation, whereas input 36 determines the count-down operation. When one of these inputs is on the other is off.

Suppose all active bistable elements 13 are initially set such that their output is at 13A and a count-up input 35 is active controlling element 33. When a pulse is applied to the input 14 of passive bistable element 12, its output switches the active element output to 13B and turns element 31 oif. However, the count-up input 35 prevents element 33 from turning on and a pulse is not sent to the next stage. When the second input pulse arrives, element 13 is switched back to output channel 13A and element 32 is turned off. Since the count-down input 36 is not active, element 34 now turns on and pulses the next stage, which brings about the switching of its element 13 to output channel 13B. At this point the binary count 2 or 2, and if additional pulses are supplied the system will continue to count up in a manner analogous to the system first described.

Now suppose the count-up input 35 is removed and the count-down input 36 is supplied. The condition of the counter is that the second stage is generating an output 13B and all other stages are reset. When the next input pulse is applied, element 13 of the first stage is switched to output 13B and element 31 is turned off. Since the count-up input 35 is not active, element 33 turns on and pulses the second stage. This switches the second stage output back to output channel 13A and turns off element 32 of the second stage. However, the count-down input 36 prevents the second stage element 34 from turning on and no pulse is transmitted to the third stage. Now the counter condition is such that the first stage has an output at 1313 and all other stages are reset. This corresponds to an output of 2 or 1, which is one less than the previous count. The system continues to count down with subsequent input pulses until the control input conditions at 35 and 36 are reversed.

FIGURE 3 is another circuit employing the count-up and cut-down features, with amplification elements 41, 42, 43 and 44 added. These additional elements are used merely as amplifiers to increase the amplitude of the pulse which is sent to the next stage. The operation of the stage shown in FIGURE 3 is otherwise identical to that of the stage shown in FIGURE 2. Thus monostable amplifying devices 41 and 43 are connected in cascade between the output channel 12A and the control port 13C. When output channel 12A is active, element 41 is switched off, thereby switching element 43 on and transmitting a positive pressure signal to control port 310. Similarly monostable amplifying devices 42 and 44 are connected in cascade between output channel 12B and control orifice 13D.

Amplification can also be obtained if desired through the elements of the count-up and count-down logic circuits, additional amplification being required only for certain applications. It is recognized that many diflerent circuit configurations may be used to provide various operating characteristics. The circuits shown in FIGURES 1, 2 and 3 have the advantage that only normally ON side of each of the monostable elements is used. Because these elements are not switched into a loaded off leg, higher gains are possible.

However, circuits using the OFF legs B of certain monostable elements can also be used to eliminate the requirement of driving two elements with one output. A circuit of this type is shown in FIGURE 4. Note that in this embodiment of the invention the control signals applied to control ports 13C and 13D of the active element are derived from the output channels 313 and 32B of monostable elements 31 and 32 respectively instead of from control channels 26 and 28. The operation of this system is otherwise functionally equivalent to that illus trated in FIGURE 2.

Aside from the particular embodiments singled out for detailed description, other embodiments including further modifications and variations will doubtless occur to those skilled in the art to which this invention pertains. The examples offered are primarily illustrative and the appended claims are intended to comprehend all such modifications and variations as are within the true spirit and scope of the invention in its broader aspects.

What is claimed is:

1. A fluid operated binary counter stage comprising:

first and second cascaded fluidic elements each having means for producing a fluid jet deflectible between bistable output channels by pressure dilferentials developed across an interaction zone and each having at least two control orifices connecting to said zone for developing said pressure differentials, means responsive to the flow of fluid in either of the output channels of said first element for introducing an increased pressure through a respective one of the control orifices of said second element to switch the fluid jet therein to a corresponding output channel, and

feedback means including a pair of jet pumps through which fluid may be entrained, each connected to a respective output channel of said second fluidic element and responsive to the flow of fluid therein for introducing a reduced pressure through a respective one of the control orifices of said first element tending to deflect the fluid jet therein to an opposite output channel, said jet pumps being connected downstream of the interaction zone of said second fluidic element, and thus not adversely affecting the flow stability in said zone,

the magnitude of the pressure differentials introduced into said first element by said feedback means being sufficient to divert the fluid jet therein into a respective output channel upon the initiation thereof but insufficient to switch the fluid jet therein to an opposite output channel durin the continuation thereof, whereby an interruption and subsequent resumption of the fluid jet in said first element switches the fluid jet in said second element to an opposite output channel.

. A fluidic bistable switching circuit comprising:

a passive bistable fluidic element including a power nozzle for issuing a discontinuous jet of fluid into an interaction zone, a pair of first control orifices for establishing selective pressure differentials transversely across said interaction zone, and first bistable output channels into which said discontinuous jet may be switched under the influence of such pressure differentials,

an active bistable fluidic element including a power nozzle for issuing a continuous jet of fluid, a second pair of control orifices for establishing selective pressure differentials transversely across said continuous jet, and second bistable output channels into which said continuous jet may be switched under the influence of said last mentioned pressure differentials,

means including control channels responsive to the condition of said first output channels for actuating selective ones of said second pair of control orifices to switch the continuous jet in said active element to an ,7 "77ii output channel corresponding to the output channel in said passive element in which said discontinuous jet flows,

a pair of jet pumps, each connected with a separate output channel of said active element downstream of said interaction zone to develop reduced pressures in response to the flow of fluid through the output channel with which itis associated, but withoutadversely aifectingthe operating characteristics of said active element, and a means including a pair of feedback channels each interconnecting a respective one of said jet pumps with a respective control orifice of said passive fluidic element, said feedback channels responding to said reduced pressures to create pressure differentials across the discontinuous jet of said passive element tending to switch'said discontinuous jet to an opposite output channel,

the pressure dilferential created across said discontinuous jet by the action of said feedback channels being suflicient to determine the bistable output channel thereof upon the initiation of said discontinuous jet but insufficient to alter the output channel thereof during the duration of said discontinuous whereby each interruption and subsequent resumption of said discontinuous jet in said passive fluidic element'switches said continuous jet to a different one of said second bistable output channels.

References Cited UNITED STATES PATENTS RICHARD B. WILKINSON, Primary Examiner. LAWRENCE R. FRANKLIN, Assistant Examiner. 

